Tapping apparatus

ABSTRACT

A TAPPING MACHINE IN WHICH A BALL SCREW AND A SPLINE SHAFT WITH A TAP SECURED AT ITS END MOUNTED TO A PRESS RAM IN A MUTUALLY MESHED RELATION THROUGH GEARING, AND AS THE PRESS RAM IS MOVED UP AND DOWN, THE UP AND DOWN STROKES OF THE PRESS ARE CONVERTED INTO ROTATION BY THE BALL SCREW, WITH THE PRODUCED ROTATING FORCE BEING TRANSMITTED TO THE SPLINE SHAFT TO THEREBY EFFECT TAPPING OPERATION.

HIDEOJ l-iosHl ET AL TAPPING APPARATUS 2 Sheets-Sheet 1 k'iied Sept. so, less a 5 F w 5 6 iv 5 I y 197R HIDEO HOSHI ETAL 3,579,687

TAPPING APPARATUS 2 Sheets-Sheet I:

Filed Sept. 30, 1968 United States Patent O 3,579,687 TAPPING APPARATUS Hideo Hoshi, 40 Minamiide Nakaodai, Yamada-cho, Nishi-ku, Nagoyashi, Japan; and Masao Washi, 3083 Oazailreda, Ikeda-cho, Kitaazumigun; and Hiroshi Yoshiki, 11-382 Higashi, Arigasaki, Matsumotoshi, both of Nagano-ken, Japan Filed Sept. 30, 1968, Ser. No. 763,856 Claims priority, application Japan, Oct. 9, 1967, 42/64,686, 42/64,687 Int. Cl. B23g 1/00 U.S. Cl. -129 4 Claims ABSTRACT OF THE DISCLOSURE A tapping machine in which a ball screw and a spline shaft with a tap secured at its end are mounted to a press ram in a mutually meshed relation through gearing, and as the press ram is moved up and down, the up and down strokes of the press are converted into rotation by the ball screw, with the produced rotating force being transmitted to the spline shaft to thereby effect tapping operation.

BRIEF SUMMARY OF THE INVENTION The present invention relates to a tapping machine for pressing and more particularly to such tapping machine in which a force in the vertical direction of the press is converted into a rotating force whereby to effect tapping.

In a press-worked article, there are a number of parts where tapping is required, and conventionally the tapping operation for such articles which require tapping has been usually practiced after the pressing operation in a separate step by a tapping machine driven by a motor.

However, according to such conventional practice, the articles must be transferred to a separate step for effecting tapping operation, so that the manufacturing process of the articles inevitably included two separate steps. Also, in a tapping machine which is not associated with pressing operation, the only means available for rotating the tap is a motor. Thus, the motor was a must in such operations.

The present invention is intended to overcome such defects and arranged so that tapping work of the articles is effected in the press-working step by utilizing up-anddown movements of a pressing machine without using a motor, or by using a pressing machine.

It is therefore an object of the present invention to provide a tapping apparatus in which, with descent of a press ram, the tip of a ball screw contacts an abutting face of a drag of the press and is pushed up thereby, and this movement is transmitted to a nut meshed with said ball screw to thereby rotate said nut, the resulting rotating force being further transmitted through a gear to a fixed spline shaft to rotate a tap, thereby effecting desired tapping on an article by the press.

It is another object of the present invention to provide a tapping apparatus in which, with descent of a press ram, the tip of a ball screw contacts an abutting face of a drag of the press and is pushed up thereby, and this movement is transmitted to a nut meshed with said ball screw to thereby rotate said nut, the resulting rotating force being further transmitted through a gear to a spline shaft, and in which a compression coil spring is arranged in the axial direction of the spline shaft so that the difference in pitch 3,579,687 Patented May 25, 1971 ICC between said ball screw and a tap secured to said spline shaft is absorbed by said compression coil spring.

It is still another object of the present invention to provide a tapping apparatus comprising a ball screw shaft provided at the cope of the press in such manner that the tip thereof contacts an abutting face of the drag of the press with descent of a press ram and is pushed up thereby, and a spline shaft arranged at a position spaced from said ball screw shaft, said ball screw shaft and said spline shaft being connected to each other by a timing belt.

It is yet another object of the present invention to provide a tapping apparatus in which an intermediate shaft having a pitch equal to the pitch difference between a ball screw and a tap is interposed between a gear of a spline shaft which rotates the tap in accordance with descent of a press ram and a gear of the ball screw, said intermediate shaft functioning to absorb the pitch difference between the ball screw and the tap so as to keep the tap free from any excess axial force. This tapping apparatus proves useful to keep the screw threads of the articles safe from mal-effects particularly when the tap pitch is small or when the material of the articles is soft and tender.

The other objects and advantages of the present invention will become clear from the following description made with reference to the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a tapping apparatus of the present invention;

FIG. 2 is a bottom view of FIG. 1;

FIG. 3 is a longitudinal sectional view of another embodiment of the present invention, in which the spline shaft and the ball screw shaft is connected by a timing belt;

FIG. 4 is a bottom view of FIG. 3;

FIG. 5 is a longitudinal sectional view showing still another embodiment of the present invention; and

FIG. 6 is a bottom view of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION Now, some embodiments of the present invention will be discussed in detail with reference to the drawings. It will be seen that a press ram 1 has mounted thereto a frame 2 which has provided therein a cylinder 4 housing a spring 3. A ball screw 5 is connected to the tip of said spring 3. The top of said ball screw 5 is projected a suitable length from the bottom of said frame 2, while the portion of said screw 5 in the frame 2 is meshed with a ball screw nut 6. Said ball screw nut 6 is securely held by a thrust bearing 7 and a cover plate 8 and has mounted near its bottom end a cogwheel 9.

It will also be noted that the press ram 1 has also mounted thereto a cylinder 10 in juxtaposition with the ball screw 5, said cylinder 10 having a central hole 11 for receiving a spring 12. A spline shaft 14 is rotatably mounted to the bottom of said spring 12 through a bearing 13. The fore end portion of said spline shaft 14 is projected from the cover plate 8, with a tap 15 being secured to the top of said portion. A cogwheel 16 is mounted around the spline shaft 14 in the frame 2, said cogwheel 16 being meshed with the cogwheel 9.

In case there is not sufiicient space for the above construction, arrangement may be made such that a timing belt 17 is provided to connect the cogwheels 9' and 16' if there is a space between the ball screw and the spline shaft 14 to which the tap is mounted, as shown in FIG. 3.

Now the discussion will be directed to the operational aspect of the present invention. Descent of the press ram 1 causes the tip of the ball screw 5 to dash against an abutting face provided on the drag of the press, and the ball screw 5 is pushed up through the spring -3. This movement causes rotation of the ball screw nut 6 held between the thrust bearing 7 and the cover plate 8 and is therefore transmitted through the cogwheels 9, 16 to the spline shaft 14, thus urging the tap 15 mounted to said shaft 14- to rotate, whereby the tap 15 is driven into the article by the spline shaft 14.

Since the pitch of the ball screw 5 does not usually coincide with the required tap pitch, the difference between the press stroke and the amount of advancement of the tap is absorbed by the spring 12.

When the ram 1 is lifted up on completion of the desired tapping operation, since the ball screw 5 is pushed up by the spring 3, the tap 15 is given a reverse rotation so that it is extracted from the screw hole.

Now the invention will be described with respect to another embodiment thereof shown in FIGS. 5 and 6. In this embodiment, the press ram 21 has mounted thereto a casing 22 which has provided at its both ends a pair of cylinders a, 25b housing springs 23a, 23b, respectively. At the foremost ends of said springs 23a, 2312 are coupled vertically movable pressing rods 24a, 24b, respectively, of which the downward stroke is defined by the check rings 26a, 26b provided at the lower parts of the cylinders 25a, 25b, respectively.

It will also be seen that an article holder member 28 having a tapping hole 27 is secured to the ends of said pressing rods 24a, 24b. A ball screw 29 provided in said casing 22 has a cogwheel 30 mounted at its top end and is, at its bottom end, meshed with a ball screw nut 31 to which is secured an end of a tamping rod 32 having its other end connected and fixed to said article holder 28. There is also mounted an intermediate shaft 33 in said casing 22, said shaft 33 having a pitch P1 which is the difference between the pitch P2 of the ball screw shaft 29 and the pitch P0 of the tap 34. At the top of the intermediate shaft 33 is mounted a cogwheel 35 meshed with the cogwheel 30 of said ball screw shaft 29. Said cogwheel 35 is also meshed with a cogwheel 38 of a spline shaft 36 to convey rotation thereto. It will also be noted that said intermediate shaft 33 is meshed with a nut 37 to which the spline shaft 36 is rotatably mounted, so that the rotation of the ball screw 29 is transmitted as vertical movements to the spline shaft 36. A tap 34 is secured at the end of the spline shaft 36.

In operation, when the press ram 21 descends, the article holder 28 abuts against the article, and the ball screw nut 31 is pushed up by the tamping rod 32 integrally secured to said holder, causing the ball screw shaft 29 to rotate. This rotation is transmitted through the cogwheels 30, 35 to the intermediate shaft 33 and thence through the cogwheel 38 to the spline shaft 36.

When the press ram descends a distance P1 after the article holder hits the article, the ball screw shaft 29 makes one rotation, with concurrent one rotation of the intermediate shaft 33, thus permitting the nut 37 to advance downward by a distance P2. Since the spline shaft 36 is rotatably supported by the nut 37, said spline shaft 36, while rotating through the cogwheel 38, makes a simultaneous downward advancement of the distance P2 through the nut 37. The tap 34 mounted to the spline shaft 36 ascends a distance P2 while making one rotation for the descent of the distance P1 of the spline shaft 21. This means that the tap advances into the article by a distance P1P2=P0, tallying with the pitch P0 of the tap 34.

When the press ram 21 ascends after tapping, the contrary operation is effected and the tamping rod 32 pulls down the ball screw nut 29, causing a rotating movement which is transmitted to the spline shaft 36 to let it make a revolving movement which permits extraction of the tap 34 from the screw hole.

Thus, in the present invention having the abovedescribed construction and function, the vertical strokes of the press are converted into revolving movements by the ball screw and the ball screw nut mounted to the press ram to thereby obtain a tapping torque. The present invention is particularly featured by provision of an intermediate shaft having a pitch equal to the difference between the ball screw pitch and the tap screw pitch, said intermediate shaft being arranged between the ball screw and the tap through a cogwheel to combine the rotation of the ball screw and turning of the tap, so that it is possible to effect tapping to a very fine extent and also perfect tapping can be attained even in an article made of soft material. In addition, to those described above, the present invention has the following advantages: it eliminates necessity of providing a motor; any desired tapping operation can be performed with ease during the pressing step; any form of tapping is effected simply by changing the intermediate shaft; tapping operation is easy and simple; and the tap position is accurately determined and correct tapping is accomplished since the accurate up and down movements of the press are converted into the revolving movements.

Whereas the invention is described and illustrated with respect to a certain preferred form, it is to be understood that many variations are possible within the spirit of the invention and as particularly pointed out in the following claims.

What is claimed is:

1. A tapping apparatus, comprising:

a press ram,

a casing,

a pair of cylinders extending between and secured to said press ram and said casing,

a pressing rod slidably mounted in each of said cylinders and having an end portion extending outwardly therefrom,

spring means in each of said cylinders in engagement with said pressing rods,

an article holder secured to said end portions of said pressing rods,

a ball screw shaft extending between and rotatably mounted on said press ram and said casing,

means for rotating said ball screw shaft when said press ram and casing are moved toward said article holder,

a spline shaft extending between and mounted on said press ram and said casing for rotary and axial movement, said spline shaft having an end portion extending through said casing towards said article holder,

at sclrew tap mounted on said end portion of said spline s aft,

an intermediate screw shaft extending between and rotatably mounted on said press ram and said casing,

means for drivingly connecting said ball screw and said intermediate shafts, and for drivingly connecting said intermediate and said spline shafts, so that said intermediate shaft and said spline shaft will be rotated in response to rotation of said ball screw shaft owing to movement of said press ram and casing toward said article holder, and I means for effecting axial movement of said spline shaft in response to rotation of said intermediate shaft, said intermediate shaft having a pitch equal to the difference between the pitch of said ball screw shaft and the pitch of said screw tap.

2. A tapping apparatus according to claim 1, in 'which said means for rotating said ball screw shaft comprises a ball screw nut meshed with said ball screw shaft, and a tamping rod extending through said casing and secured at one end to said article holder and secured at the other end to said ball screw nut, whereby when said press ram and casing are moved toward said article holder said ball screw shaft is rotated by said ball screw nut.

3. A tapping apparatus according to claim 1 wherein said means for drivingly connecting said ball screw shaft, said intermediate shaft and said spline shaft comprises a first cogwheel on said ball screw shaft, a second cogwheel on said intermediate shaft in meshing engagement with said first cogwheel, and a third cogwheel on said spline shaft in meshing engagement with said second cogwheel.

4. -A tapping apparatus according to claim 1 in which shaft comprises a threaded nut meshed with said intermediate screw shaft and rotatably connected to said spline shaft for axial movement therewith, whereby said nut and said spline shaft are moved axially in response to rotation of said intermediate shaft.

References Cited UNITED STATES PATENTS 2,314,138 3/1943 Garbe et a1 10-139 2,346,297 4/1944 Garbe 1087 2,715,233 8/1955 Clark 10139 3,162,873 12/1964 Ohme 10-139 3,348,248 10/1967 Milkert 10139 RICHARD J. HERBST, Primary Examiner E. M. COMBS, Assistant Examiner 

